判断ip地址是否合法

  下面是一个判断ip地址是否合法的算法：

#include <stdio.h>
bool IsDigit(char Digit)
{
    bool Flag = false;
    if(Digit >= '0' && Digit <= '9')
    {
        Flag = true;
    }
    return Flag;
}

bool IsFormatValid(char IP[])
{
    int DotCnt = 0;
    bool Flag = false;
    while(*IP != '\0')
    {
        if(*IP == '.')
        {
            DotCnt++;
        }
        else if(!IsDigit(*IP))
        {
            return false;
        }        
        Flag = true;
        IP++;
    }
    if(DotCnt == 3)
    {
        return Flag;
    }
    else
    {
        return false;
    }
}

bool IsValueValid(char IP[])
{
    int Len = 0;
    int Integer = 0;
    while(*IP != '\0')
    {
        if(IsDigit(*IP))
        {
            Integer = Integer*10 + *IP - '0';
        }
        else
        {
            if(Integer > 255)
            {
                return false;
            }
            Integer = 0;
        }
        IP++;
    }
}

int main()
{
    char IpAddress[30];
    printf("Please input the ip address:\n");
    scanf("%s", IpAddress);
    if(IsFormatValid(IpAddress) && IsValueValid(IpAddress))
    {
        printf("%s -> VALID", IpAddress);    
    }
    else
    {
        printf("%s -> INVALID", IpAddress);
    }
    return 0;
}